title: STAT1 regulates human glutaminase 1 promoter activity through multiple binding sites in HIV-1 infected macrophages.
abstract: Mononuclear phagocytes (MP, macrophages and microglia), the main targets of HIV-1 infection in the brain, play a pathogenic role in HIV-associated neurocognitive disorders (HAND) through the production and release of various soluble neurotoxic factors including glutamate. We have previously reported that glutaminase (GLS), the glutamate-generating enzyme, is upregulated in HIV-1 infected MP and in the brain tissues of HIV dementia individuals, and that HIV-1 or interferon-α (IFN-α) regulates human glutaminase 1 (GLS1) promoter through signal transducer and activator of transcription 1 (STAT1) phosphorylation in macrophages. However, there are multiple putative STAT1 binding sites in human GLS1 promoter, the exact molecular mechanism of how HIV-1 or IFN-α regulates human GLS1 promoter remains unclear. To further study the function of the putative STAT1 binding sites, we mutated the sequence of each binding site to ACTAGTCTC and found that six mutants (mut 1,3,4,5,7,8) had significantly higher promoter activity and two mutants (mut 2 and mut 6) completely lost the promoter activity compared with the wild type. To determine whether sites 2 and 6 could interfere with other inhibitory sites, particularly the nearby inhibitory sites 3 and 5, we made double mutants dmut 2/3 and dmut 5/6, and found that both the double mutants had significantly higher activity than the wild type, indicating that sites 3 and 5 are critical inhibitory elements, while sites 2 and 6 are excitatory elements. ChIP assay verified that STAT1 could bind with sites 2/3 and 5/6 within human GLS1 promoter in IFN-α stimulated or HIV-1-infected monocyte-derived macrophages. Interestingly, we found that rat Gls1 promoter was regulated through a similar way as human GLS1 promoter. Together, our data identified critical elements that regulate GLS1 promoter activity.
authors.affiliation: Center for Translational Neurodegeneration and Regenerative Therapy, Shanghai Tenth People's Hospital, Tongji University School of Medicine, Shanghai, China ; Laboratory of Neuroimmunology and Regenerative Therapy, University of Nebraska Medical Center, Omaha, Nebraska, United States of America ; Department of Pharmacology and Experimental Neuroscience, University of Nebraska Medical Center, Omaha, Nebraska, United States of America.
authors.forename: Lixia
authors.initials: L
authors.lastname: Zhao
authors.forename: Yunlong
authors.initials: Y
authors.lastname: Huang
authors.forename: Jialin
authors.initials: J
authors.lastname: Zheng
mesh_terms: D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D018698:Glutamic Acid / Q000096:biosynthesis; D005972:Glutaminase / Q000235:genetics*; D057809:HEK293 Cells; D015497:HIV-1 / Q000502:physiology*; D006801:Humans; D016898:Interferon-alpha / Q000494:pharmacology; D008264:Macrophages / Q000378:metabolism* / Q000821:virology*; D011401:Promoter Regions, Genetic / Q000187:drug effects / Q000235:genetics*; D051381:Rats; D050794:STAT1 Transcription Factor / Q000378:metabolism*
chemical_list: D016898:Interferon-alpha; D050794:STAT1 Transcription Factor; D018698:Glutamic Acid; C579480:GLS protein, human; D005972:Glutaminase